Artificial kidney systems usually include a dialyzer and a dialysis machine which controls the operation of the dialyzer. The dialyzer is used to treat a patient's blood so as to remove water and waste products therefrom. Such dialyzers include a semipermeable membrane which separates the blood and the dialysis solution flowing through the dialyzer. Waste product removal occurs by mass transfer through the membrane, and water removal occurs by ultrafiltration through the membrane.
Some dialysis machines operate to draw the dialysis solution through the dialyzer under a negative pressure (i.e., below atmospheric pressure). These machines normally include: (a) a negative-pressure-type pump positioned downstream of the dialyzer for drawing the dialysis solution from a source through the dialyzer; and (b) adjustable restrictions positioned upstream and downstream of the dialyzer for controlling the flow rate and the negative pressure on the dialysis solution within the dialyzer.
U.S. Pat. No. 3,878,095 Frasier et al discloses a negative-pressure-type dialysis machine of that type. A commercial machine embodying such a system is manufactured and sold by Baxter Travenol Laboratories and is identified as Proportioning Dialyzing Fluid Delivery System (5M 1352-5M 1355).
Negative-pressure dialyzers of the type sold by Baxter Travenol Laboratories under the trademark CF.RTM. dialyzer are suitable for use with such dialysis machines. This dialyzer is commonly referred to as a hollow-fiber dialyzer and includes thousands of generally axially arranged hollow fibers within which blood flows. The dialyzer has axially-spaced blood inlet and outlet ports and axially-spaced dialysis solution inlet and outlet ports. Dialysis solution flows about these fibers but in the opposite direction so as to maximize mass transfer of impurities. This type of flow is sometimes referred to as a counter-current.
Presently during dialysis, the hollow fiber dialyzer is positioned in a generally vertical attitude with blood entering the dialyzer from the top, flowing downwardly, and exiting from the bottom. Dialysis solution enters at the bottom, flows upwardly, and exits at the top. These directions of flow have been selected because of gas separation problems on both the dialysis solution and blood sides of the dialyzer.
On the dialysis solution side, this is manifested by bubbles appearing in the dialyzer, adhering to the fibers and accumulating at the top of the dialyzer due to buoyancy. The adhering and accumulating is undesirable as it reduces the efficiency of the dialyzer. The direction of dialysis solution flow was selected as upward so as to sweep as much of the separated gas out of the dialyzer as possible. Thus in order to maintain counter-current flow, the flow of blood had to be downward. On the blood side, an arterial blood trap is provided for capturing gas before it can reach the patient.
Before dialyzing a patient, a series of set-up steps are performed. These steps generally include clearing the dialyzer of gas and conditioning the dialyzer to operating temperatures, etc.
During set-up, it has been customary to flow dialysis solution into the dialyzer in the normal upward direction so as to (a) force the air on the dialysis solution side of the dialyzer out of the dialyzer and replace it with dialysis solution and render that side substantially airfree and (b) adjust the temperature of the dialyzer. The upward flow is helpful in removing air since it cooperates with the air's natural tendency to rise.
The next step is to prime the blood side, and in order to take advantage of the air's tendency to rise, the dialyzer is rotated so that the blood inlet is below the blood outlet. A saline priming solution is then flowed through the blood side of the dialyzer so as to clear the air from that side. Thereafter, the patient's blood is flowed into the dialyzer, and after the blood flow is established, the dialyzer is rotated back to its original position and dialysis can begin.
In the event an emergency causes dialysis to cease, the priming operation including reversing of positions, etc., may be repeated.
These rotation operations are inconvenient, time-consuming and cumbersome in view of all of the inlet lines, outlet lines, clamps, bubble traps, brackets, etc., that must be handled. Furthermore, in order to accommodate the rotation, the blood lines are long, the blood priming volume is large, and the amount of blood outside the patient is large.
In West German Offenlegungsschrift No. 2,824,818 filed on June 7, 1978 and laid open on Dec. 21, 1978, there is disclosed another form of a hollow-fiber dialyzer having a single blood connection and a single dialysis solution connection with connectors which can be reversed to give upward blood priming or back flushing on the dialysis solution side. In the normal operation, that dialyzer is maintained in one position and blood flows downwardly and dialysis solution flows upwardly.
However, the use of that dialyzer does not solve the problem of positioning and repositioning of the typical hollow-fiber dialyzer which has a pair of spaced blood ports and a pair of spaced dialysis solution ports.
It is therefore an object of this invention to provide a dialysis machine and dialyzer system wherein the rotation or positioning and repositioning of the dialyzer during set-up in order to prime and condition the dialyzer is not necessary.
In addition to the CF.RTM. dialyzer, there is another negative-pressure type of dialyzer known as a HD.TM. capillary film dialyzer. This dialyzer is sold by Baxter Travenol Laboratories under its code M1780 and M1781.
In the HD.TM. dialyzer, both the blood inlet and dialysis solution inlet are located at the bottom of the dialyzer and respective outlets are at the top of the dialyzer so that both the blood and dialysis solution flow upwardly. It will be noted that in the HD.TM. dialyzer the blood flows from bottom-to-top, while in the CF.RTM. dialyzer, blood flows from top-to-bottom. Presently this difference in flow direction requires that different flow line connections-be made by the operator.
It is therefore another object of this invention to provide a dialysis machine capable of operation with either the hollow-fiber dialyzer, the capillary-film dialyzer, or other negative-pressure-type dialyzers so as to avoid different flow line arrangements.
These and other objects of this invention will become apparent from the following description and appended claims.